1: Structure of Solid Surfaces
- Page ID
- 25348
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)In most technological applications, metals are used either in a finely divided form or in a massive, polycrystalline form. At the microscopic level, most materials, with the notable exception of a few truly amorphous specimens, can be considered as a collection or aggregate of single crystal crystallites. The surface chemistry of the material as a whole is therefore crucially dependent upon the nature and type of surfaces exposed on these crystallites.
- 1.1: Introduction
- This page discusses the use of metals in different forms and their structural characteristics at the microscopic level. It emphasizes the importance of surface chemistry due to the presence of single crystallites in most materials. The study of surface properties involves analyzing well-defined surfaces created from macroscopic single crystals, focusing on low-index surfaces. A thorough understanding of bulk crystal structures is essential to predict atomic arrangements on these surfaces.
- 1.2: Miller Indices (hkl)
- This page explains Miller Indices, which are used to represent crystal plane orientations through their intercepts with crystallographic axes. It details the procedure for calculating these indices, including identifying intercepts, converting to fractional coordinates, and taking reciprocals.
- 1.3: Surface Structures- fcc Metals
- This page discusses the face-centered cubic (fcc) structure, focusing on the (100), (110), and (111) surfaces of significant metals like Pt, Rh, and Pd. It details their atomic arrangements and coordination numbers: (100) has 4-fold symmetry and a coordination number of 8, (110) is less packed with a coordination number of 7, and (111) is close-packed with a coordination number of 9. These surface architectures influence the metals' chemical reactivity and interactions with adsorbates.
- 1.4: Surface Structures- hcp Metals
- This page covers the hexagonal close-packed (hcp) structure in metals such as Co, Zn, Ti, and Ru, emphasizing Miller Index notation with a unique four-digit system. It describes the (0001) surface aligned with the c-axis, highlighting its atomic arrangement, where all surface atoms have a coordination number of 9. The surface's smoothness and various adsorption sites—on-top, bridging, and hollow—are also discussed, providing insights into the structural and chemical properties of hcp surfaces.
- 1.5: Surface Structures- bcc metals
- This page explores the body-centered cubic (bcc) structure of metals, highlighting the characteristics of its (100), (110), and (111) surfaces. Each surface is described in terms of symmetry and atomic density, with (100) featuring 4-fold symmetry and low coordination, (110) possessing rectangular symmetry and higher atomic density, and (111) displaying 3-fold symmetry with multiple atomic layers.
- 1.6: Energetics of Surfaces
- This page discusses the energetically unfavorable nature of surfaces due to their positive free energy of formation, linked to bond-breaking energy during surface creation. It highlights methods to minimize surface free energy by reducing exposed area and exposing low-energy surface planes. The text also notes that high surface energy systems may face kinetic barriers preventing transition to lower energy states at low temperatures, leading to metastability.
- 1.7: Relaxation and Reconstruction
- This page explores the concepts of relaxation and reconstruction of surface atoms to reduce surface free energy. Relaxation involves minor rearrangements that maintain periodicity and symmetry, while reconstruction involves significant atomic displacements, altering these properties, especially in less stable metals and semiconductors. Adsorption can influence these processes, leading to adsorbate-induced reconstruction.
- 1.8: Particulate Metals
- This page discusses the prevalence of polycrystalline metallic structures over macroscopic single crystals in technology, highlighting how individual crystallite properties influence surface characteristics. It notes the behavior of small supported metal catalysts and their typical shapes, which optimize surface area and low-energy surfaces.
- 1.9: Other Single Crystal Surfaces
- This page explores the complexity of single crystal surfaces, highlighting high index surfaces with unique features such as terraces and steps that affect atomic coordination and catalytic properties. It details the irregular morphology of real vicinal surfaces and discusses compound crystal surfaces, showing how surface structures can mirror bulk properties but may deviate due to factors like surface reduction and segregation.